When paints are applied manually or automatically to articles, some of the stream of paint, which in general contains both solids and solvents and/or binders, is not applied to the article. This portion of the stream is called overspray in the art. The overspray is taken up by the air stream in the spray booth and fed to a separation process.
In particular in the case of plant having a relatively high paint consumption, for example plant for painting vehicle bodies, wet separation systems are preferably used. In the wet separators known from the market, water flows, together with the exhaust air in the booth coming from above, to a nozzle that accelerates the flow of air. In this nozzle, the exhaust air flowing through from the booth is subjected to turbulence with the water. During this procedure, the particles of overspray are largely transferred to the water, with the result that the air leaves the wet separator substantially cleaned, and the particles of paint overspray are in the water. They can then be recovered therefrom or disposed of.
In the case of known wet separators, relatively large amounts of energy are needed to circulate the quite considerable quantities of water required. Because of the heavy use of paint-binding and adhesive-removing chemicals and because of the disposal of paint sludge, preparing the rinsing water is cost-intensive. Furthermore, the air takes up a very considerable amount of moisture as a result of its intensive contact with the rinsing water, and this in turn results in high energy consumption for the preparation of air in the circulation operation.
In contrast, in the case of devices known from the market of the type mentioned at the outset, separation is carried out in dry conditions, in that particles of paint overspray which are carried along by the exhaust air from the booth which flows past are ionised by the electrode means and, because of the electrical field that is formed between the separating surface and the electrode means, migrate to the separating surface and are separated off there. The particles of paint overspray which adhere to the separating surface can then for example be stripped mechanically therefrom and transported away.
Strippers of this kind have a very effective cleaning action. For continuous operation, however, it must always be ensured that it is possible for a sufficiently strong electrical field to be formed between the separating surface and the electrode means, and this is only possible up to a certain film thickness of paint overspray on the separating surface, since a film of this kind has an insulating action. The continuous removal of the paint overspray from the separating surface that is required entails highly complex structural measures, however, and can be susceptible to faults.
The present invention is directed to resolving these and other matters.